The eastern mosquitofish (Gambusia holbrooki) is a species of freshwater fish, closely related to the western mosquitofish, Gambusia affinis. It is a member of the family Poeciliidae of order Cyprinodontiformes. The eastern mosquitofish is native to the eastern and southern United States from Florida to Pennsylvania and inland to Alabama and Tennessee, while the western mosquitofish has a larger distribution throughout the United States. Description The Eastern mosquitofish is a small, light-colored fish with semitransparent fins. The females usually have a black stripe near their eye area and light spots can be seen on the caudal and dorsal fins of both sexes. Due to its similar size, shape, and reproductive habits, it can easily be mistaken for a guppy. Generally, males reach and females . These fish are a livebearer species, and as such, the females are larger and more rounded than the males. Pregnant females are also easily recognizable by their gravid spot; a darker area on their bellies where they hold the fry. Mosquitofish may have a melanistic color pattern with black spots, resembling a dalmatian. This could result in its being misidentified as another species. Similar species In its native range, eastern mosquitofish may be confused with the western mosquitofish (Gambusia affinis) or the sailfin molly (Poecilia latipinna). In eastern Australia, the female and juvenile local Pacific blue-eye (Pseudomugil signifer) are similar in appearance but have a forked tail fin. Taxonomy and naming French naturalist Charles Frédéric Girard described the species in 1859. The genus Gambusia comes from the Cuban term, "Gambusino", which means "free-lance miner". Common names include eastern mosquitofish, plague minnow and eastern gambusia. The identity of the person honored in the specific name is uncertain but is thought to be the physician and naturalist John Edwards Holbrook (1796-1871). Diet G. holbrooki is considered a planktivorous species which consumes algae and detritus. Feeding habits seem to change based on maturity and mating season. Gambusia holbrooki will, if need arises, switch food sources to survive. With an increase of competition, this species will switch from a diet rich in phytoplankton, algae, and detritus to one consisting of zooplankton, invertebrates, the larvae of many other fish and amphibian species, and plant-associated animals. The main source of competition for G. holbrooki seems to be an increase of its own species and other planktivorous species. The main problem with this is, as mentioned before, it will change its diet;